To　improve　the　photoelectric　conversion　efficiency　of　the　single　junction　amorphous　silicon　(a-Si)　solar　cells　and　alleviate　the　increasingly　serious　energy　and　environmental　problems,　Yb3+,　Ho3+　doped　NaYF4　phosphors　were　prepared　by　high　temperature　solid　state　method.　The　transformation　of　Yb3+　and　Ho3+　co-doped　NaYF4　phosphors　on　photoluminescence　were　studied　under　the　heat　treatment　process,　and　the　effect　of　the　transformation　on　surface　morphology　and　phase　structure　were　analyzed.　The　samples　were　investigated　by　X-ray　diffraction　(XRD),　scanning　electron　microscopy　(SEM)　and　photoluminescence　(PL)　testing.　Results　show　that　under　the　980　nm　excitation,　three　up　conversion　emission　bands　541,649　and　750　nm　are　clearly　resolved.　The　material　can　be　used　for　promoting　the　conversion　efficiency　of　a-Si　solar　cells.　Further　study　shows　that　by　changing　the　annealing　temperature　to　modulate　the　surface　morphology　and　phase　structure　of　the　samples,　their　PL　density　can　be　enhanced　up　to　a　great　extent　nearly　40　times,　which　is　the　strongest　PL　density　of　these　samples　at　an　annealing　temperature　of　700℃.　©　2016,　Editorial　Department　of　Journal　of　Beijing　University　of　Technology.　All　right　reserved.